A computer network is a collection of interconnected computing devices that exchange data and share resources. In a packet-based network the computing devices communicate data by dividing the data into small blocks called packets. Certain devices within the network, such as routers and switches, maintain routing and/or forwarding information that describe paths through the network. In this way, the packets may be individually transmitted across the network from a source device to a destination device. The destination device extracts the data from the packets and assembles the data into its original form. Dividing the data into packets enables the source device to resend only those individual packets that may be lost during transmission.
Examples of computer networks include enterprise networks, branch networks, service provider networks, home networks, virtual private networks (VPNs), local area network (LANs), virtual LANs (VLANs) and the like. In any case, the computer networks may enable remotely located sources and receivers to share data. In some cases, the computer network may be configured to support multicast traffic, such as Internet Protocol Television (IPTV), desktop conferences, corporate broadcasts, music and video web casts, and other forms of multimedia content. For example, the computer network may utilize protocol independent multicast (PIM) as a multicast routing protocol to build distribution trees through the computer network for the transmission of multicast traffic between sources and receivers within customer sites for particular multicast groups. PIM may operate in several different modes, including Dense Mode (DM), Sparse Mode (SM) in Source-Specific Multicast (SSM) mode or Any Source Multicast (ASM) mode, and Bidirectional (BIDIR) mode.
In addition, the computer network may be configured to support multicast VPNs (MVPNs) to enable Internet Protocol (IP) multicast traffic to travel between sources and receivers within customer sites. For one or more MVPNs, provider edge (PE) routers coupled to the customer sites may conceptually build a multicast tree to carry multicast traffic from a multicast source through the public network so that the customer sites receive the multicast traffic as if the customer sites were directly attached to the same private network as the source.